Epistemic Closure is a somewhat obscure philosophical concept which has been appropriated (quite inappropriately) by some on the right who have wandered from the path of true belief to describe what we heathens like to call the the right-wing echo chamber. The key idea is that it's quite possible to live in a world of Fox News, Glenn Beck, Drudge and talk radio and get lots of reinforcement for beliefs which have no grounding in fact, or perhaps without suspecting that most others regard these beliefs as nuts.
Richard Feynman liked to say that the first duty of the scientist is to doubt his own theories. Several religions take an opposite point of view, insisting that the highest virtue is to believe in the face of lack of evidence or even in the presence of contradictory evidence. These, of course, are the people who mark themselves off from those who belong to what they scornfully call the "reality based community." The Republican Party (I think) has embraced this "we create our own reality" notion for many years, and it rose up to bite them this election - in just the nasty way that the real reality always likes to. In the face of plenty of evidence, they seem to have clung to the notion that (almost) all the polls really were wrong and were apparently genuinely shocked when they lost.
Of course Obama made a somewhat similar type of mistake when he blew the first debate. Despite the evidence that Romney was a reasonably skilled and highly experienced debater with a habit of making stuff up out of whole cloth, Obama was so blinded by his personal contempt for the man that he failed to prepare effective counters. Instead of an echo chamber though, he got a thorough spanking by those who were forced to explain how badly he had screwed up. If Michelle's face post debate was any clue, she was first in line with the bad news.
Andrew Sullivan reports some reflections on the psychological roots of our tendency to lock ourselves into various forms of reality denial from Nobel Economist Daniel Kahneman:
These notions are also fundamental to Jonathan Haidt's book The Righteous Mind which I have frequently written about previously.